1. Field of the Invention
The present invention relates generally to an apparatus and method for adjusting a beam pattern in a communication system supporting a Beam Division Multiple Access (BDMA) scheme, and more particularly, to an apparatus and method for adjusting a beam pattern for an array antenna including at least two antenna elements in a communication system supporting a BDMA scheme.
2. Description of the Related Art
Generally, when a user holds a portable terminal in their hand, a characteristic of an antenna used in the portable terminal can change due to an electromagnetic characteristic which is associated with the user's body, such as the hand, head, or other body part of the user's body.
Due to this change of the antenna characteristic, an impedance matching between an antenna side and a system side is not performed for the antenna used in the portable terminal, that is, an impedance mismatch occurs in the antenna used in the portable terminal, which can lead to degradation of communication performance of the portable terminal.
Various schemes for preventing degradation of antenna performance due to impedance mismatching have been proposed, and a typical scheme is an automatic impedance matching scheme.
The automatic impedance matching scheme is a scheme of detecting a Voltage Standing Wave Ratio (VSWR) value which includes a magnitude of a signal and a phase of a signal to automatically match an impedance of an antenna frequency based on the detected VSWR value. Typically, the portable terminal includes a signal detector, a controller, and a variable capacitor. The signal detector detects a VSWR signal which is received through the antenna of the portable terminal, and the controller adjusts a value of the variable capacitor so that the impedance of the antenna frequency becomes an impedance that is matched to a desired transmission/reception frequency.
In the automatic impedance matching scheme, the value of the variable capacitor is adjusted, so the impedance of the antenna frequency in the portable terminal may have an optimized value.
The automatic impedance matching scheme ensures that the impedance of the antenna frequency has an optimized value. However, when the automatic impedance matching scheme is used, the following situations may occur.
First, the human body has an electromagnetic characteristic which changes according to a frequency. More particularly, the human body has an electromagnetic characteristic of a type of dielectric substance in a frequency band which is used in a general portable terminal. However, in a relatively high frequency band, e.g., a frequency band which is greater than or equal to 10 GHz, such as a communication system supporting a BDMA scheme, the human body has an electromagnetic characteristic similar to a conductor.
In a conventional communication system, an impedance change is usually minor, and it is, therefore, possible to perform an impedance matching operation in which an electromagnetic characteristic due to the human body is considered using a variable capacitance, and the like. However, in a relatively high frequency band, e.g., a frequency band which is greater than or equal to 10 GHz, it is difficult to guarantee performance thereof even though the automatic impedance matching scheme is used.
Second, a communication system supporting a BDMA scheme uses an array of antennas in order to increase communication throughput. Generally, the array of antennas, in which a plurality of antenna elements are arranged, is used for increasing directivity, and controls a beam to radiate in a specific direction by adjusting a phase of each antenna element.
However, since the automatic impedance matching scheme targets impedance matching for an individual antenna not impedance matching for a plurality of antenna elements, the automatic impedance matching scheme does not consider various situations that may occur in an array of antennas, e.g., distortion of a beam, and the like.